Ignition coil



June 30, 1931.

IGNITION COIL Filed Feb. 23 192 A. ELLWANGER 1,812,520 I Patented June 30, 1931 UNITED STATES PATENT OFFICE ADOLF ELLWAINGER, OF STUTTGART, GER-MANY, ASSIGNOR 1'0 ROBERT BOSCH AKTIENGESELLSCHAFT, OF STUTTGART, GERMANY IGNITION coIL Application filed February 23, 1928, Serial The present invention relates to an ignition coil with an iron yoke suitable for the battery ignition mechanism in internal combustion engines, i. e., an ignition coil in which 5 the path of the lines of force of the core is closed by an iron ring.

The principal feature of the invention consists in forming the annular iron yoke of two' parts, consisting of rectangular strips of.

sheet metal of equal or unequal length, the ends of the core resting between the end faces of the semi-annular members. 7

It should be noted that the two features are already known per se in a few advantageous combinations. t has already been proposed to use two semi-annular members as the iron yoke, consisting of bent rectangular strips of sheet metal. The core is arranged so as to connect the centres of the two semi-annular members in the form of a bridge. This arrangement is unfavourable from the electrical point of view as the lines of magnetic force must pass through the strips of metal at right angles to their laminations.

On the other hand it is not novel to arrange the core between the two annular members, so that its ends rest between the two end faces of the annular member. In this known construction, however, the annular members 3 consisted of laminae stamped in the shape of nearly semi-annular rings for the purpose of correct electrical lamination, whlch is disadvantageous for manufacturing reasons. On stamping the semi-annular laminae more than 50% of the metal is wasted, which is absolutely avoided when cutting rectangular pieces. Further, cutting of rectangular strips is also much more simple than stamping curved members.

One form of construction of the invention is shown in the drawings Figure 1 is a cross section through the ignition coil, along the line m-a: in Figure 2, in which the winding'is shown in dotted lines and Figure 2 is a vertical section along the line y-y in Figure 1.

The core a which carries the i ition coil 1) consists of rectangular strips o s heet metal, which are superimposed on one another and N0. 258,413, and in Germany April 2, 1927.

united to form a bundle by means of rivets c. The ends of the two outside strips are bent at right angles,'so as to form flanges d between which the coil 12 is held. The core a is supported by bolts 0 which are shown by dotted lines in Figure'Q.

The path for the lines of force is closed through two semi-annular members f of laminatediron. The separate layers of the semi-annular members also consist of rectangular strips of sheet metal, which can be cut from sheets similarly as the laminae of the core a. The bundles f or the laminae forming the same are bent into semi-circular shape and are held together by rivets which serve at the same time to secure the undles on the inside of the protective casing h.

The strips of metal forming the semiannular member f-may be of the same length; in this case, however, the distance between their'ends and the core a varies as the individual laminae of a bundle have different radii of curvature.

In order to prevent the ends of some of the laminae projecting too far, it is advisable to form the bundle of two or more minor bundles of laminae of different lengths, the laminae in each minor bundle having the same length. In this case, two or more short projections are formed in the ends of the two minor bundles of laminae. In the form of construction shown,'each minor bundle consists of two minor bundles of laminae the laminae of the inner bundles being shorter than those in the outer bundles.

Relatively large gaps are left in the usual manner between the ends of the semi-annular members and the core a. As can be seen, the lines of force can pass over, both at the ends of the laminw of the core and also those of the semi-annular members, parallel to the lamination, which is desirable in order to obtain a. good electrical effect.

I claim:

1. An ignition ooil for battery ignition apparatus in internal combustion engines comprising in combination a yoke comprising a plurality of bundles of bent rectangular strips of sheet metal, all the laminae in a bundle being of the same length, the lengths of the laminae in the respective bundles bemg substantiallv proportional to the average radius of curvature of each bundle. and a core the ends of which are located between the ends of the yoke and spaced therefrom.

An ignition coil for battclii' igmtionapparatus in internal combustion engines comprising a pair of scmi-aunular yoke members each coinpr'ising a plurality 'ofrcctaugular;

strips of sheet metal bent-into :u-cuate form and overlapped in minor bundles of dlfi erent lengths each minor lndlc being formed by a number of strips of equal length, the'lengths of the laminae in the respective bundles being substantially proportional to the average radius of curvature of each bundle, and a core the ends of which are located between the-ends of the yoke members and spaced therefrom.

3. An ignition coil consisting of a yoke including a pair of separate main bundles of laminae, each main bundle comprising a plurality of minor bundles of bent rectangular strips of sheet metal of equal length forming the laminae, the different minoribundles in each main bundle being of difi'erent lengths, I

a core, the ends of which are located between the ends of the bundles, a protective casing for the coil in the form of a cylinder having continuous straight sides and a bolt passing transversel throu h the lamina: of each main bundle, an the side of said protective casing binding the two main bundles to the casing separately andspaced apart.

4. An ignition induction coil' comprising a substantially straight laminated core and a semi-annular laminated yoke formed of a plurality of concentric semi-cylindrical laminae, said core being spaced frombut overlapping the butt ends of said yoke and haying its plane of lamination parallel to the plane of the yoke.

In testimony whereof I have hereunto allixed my signature.

ADOLF ELLWANGER. 

